In recent years, pneumatic and vacuum systems have been developed for removing the contents of railway hopper cars. Other systems use rack and pinion assembly to open and close the gate valve. Some of these systems have been designed to operate in conjunction with a gate valve that is mounted on the bottom of the hopper and through which the materials are discharged.
These conventional gate valve systems that require complex rack and pinion arrangements, and/or creating a pressure differential and the like, are more difficult to manufacture and employ. Therefore it is highly desirable to construct an easily operable gate valve mechanism with few moving parts and is easy to manufacture. It is also desirable to provide the capability to operate the gate valve from both sides of the hopper car and to provide a variable-sized opening to efficiently discharge the contents of the hopper car.